Weight paint color influence in Blender
When dealing with robotic and mechanical animation, you should assign every vertex of torso to the torso bone  ONLY, the hip vertices to the hip bone ONLY, and so on. As long as a group of vertices are assigned to a bone/vertex group ONLY, they will move exactly with their bone, without distortions and deformations (and the value of the weight is not important, you can set it to 1.0, but any other value is OK). Deformations will occour when there are difference between the weights of different vertices, which tipically occour when using automatic weighting. So use instead parenting with "empty groups" option, then select the hip vertex group, select all hip vertices and click "assign" under the vertex group properties tab. Do the same for all the others vertex groups.